Element contamination of the Orange-Vaal River basin, South Africa: a One Health approach.

Numerous low-income groups and rural communities depend on fish as an inexpensive protein source worldwide, especially in developing countries. These communities are constantly exposed to various pollutants when they frequently consume polluted fish. The largest river basin in South Africa is the Orange-Vaal River basin, and several anthropogenic impacts, especially gold mining activities and industrial and urban effluents, affect this basin. The Department of Environment, Forestry and Fisheries in South Africa has approved the much-anticipated National Freshwater (Inland) Wild Capture Fisheries Policy in 2021. The aims of this study were (1) to analyze element concentrations in the widely distributed Clarias gariepinus from six sites from the Orange-Vaal River basin and (2) to determine the carcinogenic and non-carcinogenic human health risks associated with fish consumption. The bioaccumulation of eight potentially toxic elements (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) was assessed in C. gariepinus from sites with different anthropogenic sources. The human health risks were determined to assess the potential risks posed by consuming contaminated C. gariepinus from these sites. Carcinogenic health risks were associated with fish consumption, where it ranged between 21 and 75 out of 10,000 people having the probability to develop cancer from As exposure. The cancer risk between the sites ranged between 1 and 7 out of 10,000 people to developing cancer from Cr exposure. A high probability of adverse non-carcinogenic health risks is expected if the hazard quotient (HQ) is higher than one. The HQ in C. gariepinus from the six sites ranged between 1.5 and 5.6 for As, while for Hg, it was between 1.8 and 5.1. These results highlight the need for monitoring programs of toxic pollutants in major river systems and impoundments in South Africa, especially with the new fisheries policy, as there are possible human health risks associated with the consumption of contaminated fish.

Effects of river regulation on aquatic invertebrate community composition: A comparative analysis in two southern African rivers.

While natural floods play a crucial role in shaping the composition of aquatic communities, the most rivers worldwide are regulated or dammed for anthropogenic purposes, resulting in alterations to the biological and chemical composition of these ecosystems. Studies have demonstrated various negative effects of river regulation on aquatic invertebrate communities globally. However, there is a scarcity of research in Africa, despite its vulnerability to anthropogenic impacts. This study aimed to compare aquatic invertebrate communities in the Phongolo River, an impacted regulated river, and the Usuthu River, a less impacted unregulated river, in South Africa. It further aimed to ascertain whether Lake Nyamithi, a naturally saline lake receiving water from both of the aforementioned systems, exhibited a stronger similarity to one of the two rivers in terms of its aquatic invertebrate composition. Aquatic invertebrate and water samples were collected from 2012 to 2018 over several surveys. The Usuthu River demonstrated a diverse and sensitive aquatic invertebrate community, emphasising its high conservation value. The Phongolo River demonstrated effects of anthropogenic impact, with taxa more resilient to changes in water quality and flow compared to the Usuthu River. Mismanagement and excessive water use may lead to the loss of any remaining sensitive aquatic invertebrate communities in this river. The presence of invasive molluscan in the Phongolo River and Lake Nyamithi also poses a threat to the native aquatic invertebrate communities. These invasive species are currently absent from the Usuthu River although other invasive species, such as the Australian redclaw crayfish, are found in both river systems. Lake Nyamithi displayed a unique aquatic invertebrate community, distinct from both rivers and their floodplains. This study provides important baseline information on the Usuthu River's aquatic invertebrates and emphasises the need to maintain adequate water flow in rivers and floodplains to protect biodiversity and sensitive species.

Review of scientific literature on available methods of assessing organochlorine pesticides in the environment.

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs) widely used in agriculture and industry, causing serious health and ecological consequences upon exposure. This review offers a thorough overview of OCPs analysis emphasizing the necessity of ongoing work to enhance the identification and monitoring of these POPs in environmental and human samples. The benefits and drawbacks of the various OCPs analysis techniques including gas chromatography-mass spectrometry (GC-MS), gas chromatography-electron capture detector (GC-ECD), and liquid chromatography-mass spectrometry (LC-MS) are discussed. Challenges associated with validation and optimization criteria, including accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ), must be met for a method to be regarded as accurate and reliable. Suitable quality control measures, such as method blanks and procedural blanks, are emphasized. The LOD and LOQ are critical quality control measure for efficient quantification of these compounds, and researchers have explored various techniques for their calculation. Matrix interference, solubility, volatility, and partition coefficient influence OCPs occurrences and are discussed in this review. Validation experiments, as stated by European Commission in document SANTE/11813/2017, showed that the acceptance criteria for method validation of OCP analytes include ≤20 % for high precision, and 70-120 % for recovery. This may ultimately be vital for determining the human health risk effects of exposure to OCP and for formulating sensible environmental and public health regulations.

Element Concentrations in Muscle and Liver Tissue of Two Eel Species from the Incomati River, Mozambique.

Many rural communities in Mozambique get their income from fisheries, as well as consume fish as an inexpensive source of protein. In Mozambique, fish consumption from small-scale fisheries dependent families can range between 60 and 150 kg/person/year. Anguillid eels have important social value to vulnerable local communities in the Incomati Basin. Anguillid eels in the lower Incomati Basin are targeted for consumption, as well as cultural rituals by traditional healers. The aim of the present study was to determine trace element concentrations in environmental matrices, bioaccumulation patterns in muscle and liver tissue of two Anguilla species (Anguilla mossambica and Anguilla marmorata), as well as the chronic health risk these elements pose to regular consumers in the lower Incomati River. Bioaccumulation of elements from the water had a higher effect on both muscle and liver tissues, where only the bioaccumulation of Pb in the sediments played a major role. From the human health risk assessment, Hg pose non-carcinogenic risk, whereas As, Cr, and Ni pose carcinogenic risks.

A stable isotope analysis of the dietary patterns of the aquatic apex predator, the African tigerfish (Hydrocynus vittatus).

Stable isotope analyses, specifically δ13 C and δ15 N, are useful tools increasingly used to understand ecosystem function, food web structures, and consumer diets. Although the iconic tigerfish Hydrocynus vittatus is regarded as an apex predator in southern African freshwater systems, little information is available regarding their feeding behavior and how this may change with growth or differ between ecosystems, with most information stemming from stomach content analyses (SCA). The aim of the present study was to address this lack of information through a baseline study of the diet of large and small tigerfish in various lentic and lotic ecosystems in South Africa using stable isotope methods. Fish and various food web components and food sources were collected from two river and two lake ecosystems in South Africa. The δ13 C and δ15 N values for all samples were determined and multivariate analyses and Bayesian analytical techniques applied to determine the feeding ecology of H. vittatus and how this may differ with size and habitat type. Analyses revealed a substantial difference in the type and abundance of food sources contributing to the diet of H. vittatus between ecosystems, most prominently between the lotic systems, where less dietary specialization was observed, and lentic systems where more specialization was observed. Furthermore, there was a distinct difference in diet between small and large tigerfish, especially in the lotic system, indicating an ontogenetic diet shift as tigerfish grow and further supporting previous SCA studies. This is the first study of its kind on the African continent for H. vittatus and the findings illustrate the value of stable isotope analysis in providing in-depth information into the feeding ecology of consumers and how this may differ between size classes and habitat types.

Using Confocal Microscopy and Pigment Analyses to Detect Adverse Insecticide Effects in non-target Freshwater Diatom species - a proof-of-concept Using Nitzschia palea.

The persistence of insecticides in aquatic environments is a cause of concern and to date hardly any studies have focused on the effects that DDT and deltamethrin have on non-target freshwater diatom communities. The application of diatoms in ecotoxicological studies is well acknowledged and therefore this study used laboratory bioassays to determine the effects that DDT and deltamethrin have on a monoculture of a diatom indicator species, Nitzschia palea. The insecticides affected the morphology of chloroplasts at all exposure concentrations. These effects were a maximum reduction in chlorophyll concentrations (4.8% and 2.3%), cell viability (51% and 42%), and increases in cell deformities (3.6% and 1.6%) following exposure to DDT and deltamethrin respectively. Based on the results we propose that methods, such as confocal microscopy, chlorophyll-α analysis and cell deformities are useful tools in assessing the effects of insecticides on diatoms.

Influence of different functionalized CdTe quantum dots on the accumulation of metals, developmental toxicity and respiration in different development stages of the zebrafish (Danio rerio).

Introduction: The bioaccumulation and differential effects of cadmium tellurium quantum dot (CdTe QDs) nanomaterials with different functional groups are poorly understood in aquatic organisms. This study aimed to investigate the metal uptake, developmental effects, and respiratory effects of CdTe QDs with different functional groups (COOH, NH3, and PEG) on zebrafish embryos. Methods: Zebrafish embryos were exposed to carboxylate (COOH), ammonia (NH3), and polyethylene glycol (PEG) functionalized CdTe QDs at nominal concentrations of 0.5, 2, 4, 6, and 20 mg QDs/L. The materials were characterized in E3 exposure media and the metal uptake, developmental effects, and respiratory effects of zebrafish embryos were recorded. Results: The total Cd or Te concentrations in the larvae could not be explained by the metal concentrations or dissolution of the materials in the exposure media. The metal uptake in the larvae was not dose-dependent, except for the QD-PEG treatment. The QD-NH3 treatment caused respiration inhibition at the highest exposure concentration and hatching delays and severe malformations at low concentrations. The toxicities observed at low concentrations were attributed to particles crossing the pores in the chorion, and toxicities at higher concentrations were linked to the aggregation of particle agglomerates to the surface of the chorion impairing respiration. Developmental defects were recorded following exposure to all three functional groups, but the QD-NH3 group had the most severe response. The LC50 values for embryo development of QD-COOH and QD-PEG groups were higher than 20 mg/L, and the LC50 of the QD-NH3 group was 20 mg/L. Discussion: The results of this study suggest that CdTe QDs with different functional groups have differential effects on zebrafish embryos. The QD-NH3 treatment caused the most severe effects, including respiration inhibition and developmental defects. These findings provide valuable information for understanding the effects of CdTe QDs on aquatic organisms and highlight the need for further investigation.

Investigation of dichlorodiphenyltrichloroethane (DDT) on xenobiotic enzyme disruption and metabolomic bile acid biosynthesis in DDT-sprayed areas using wild rats.

Dichlorodiphenyltrichloroethane (DDT) is an organochlorine insecticide used worldwide. Several studies have reported the toxic effects of DDT and its metabolites on steroid hormone biosynthesis; however, its environmental effects are not well understood. This study examined wild rats collected in DDT-sprayed areas of South Africa and quantified plasma metabolites using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS). Fold change analysis of the metabolome revealed the effect of DDT on bile acid biosynthesis. Gene expression of the related enzyme in rat liver samples was also quantified. Significant association was found between DDT and gene expression levels related to constitutive androstane receptor mediated enzymes, such as Cyp2b1 in rat livers. However, our results could not fully demonstrate that enzymes related to bile acid biosynthesis were strongly affected by DDT. The correlation between DDT concentration and gene expression involved in steroid hormone synthesis in testis was also evaluated; however, no significant correlation was found. The disturbance of metabolic enzymes occurred in rat liver in the target area. Our results suggest that DDT exposure affects gene expression in wild rats living in DDT-sprayed areas. Therefore, there is a need for DDT toxicity evaluation in mammals living in DDT-sprayed areas. We could not find an effective biomarker that could reflect the mechanism of DDT exposure; however, this approach can provide new insights for future research to evaluate DDT effects in sprayed areas.

Morphological and molecular characterisation of Alella igillimpethu n. sp. (Copepoda: Siphonostomatoida: Lernaeopodidae) parasitising the southern African endemic intertidal klipfish, Clinus superciliosus.

Lernaeopodidae Milne Edwards, 1840, is an ecological and economically important fish parasite family of copepods (Crustacea: Copepoda), consisting of 48 genera with 334 valid species. To date, approximately 17 genera have been documented from both teleost and elasmobranch hosts from South African marine waters. As part of parasitological surveys targeting parasites of the endemic intertidal klipfish, Clinus superciliosus (Linnaeus) (Clinidae) along the South African coast, a species of Lernaeopodidae was discovered on the gills of this host. Alella igillimpethu n. sp. is described from Clinus superciliosus from Langebaan marina on the west coast of South Africa, with a prevalence of 42.1% and mean intensity of 2.9 (ranging from 1-13). Morphological identification was done using light and scanning electron microscopy and the species description was generated with the aid of DEscription Language for TAxonomy (DELTA) software. The mitochondrial cytochrome c oxidase subunit 1 (COI) region, as well as partial 18S and 28S ribosomal RNA genes confirmed the classification within the family Lernaeopodidae. This is the first report of Lernaeopodidae from C. superciliosus, or in fact any member of Clinidae, as well as the first molecular characterisation of any marine lernaeopodid infecting teleost fish from South Africa. This study contributes valuable genetic and morphological data for this copepod family, as well as new host and distribution records.

High element concentrations are not always equivalent to a stressful environment: differential responses of parasite taxa to natural and anthropogenic stressors.

Environmental parasitology developed as a discipline that addresses the impact of anthropogenic activities related to the occurrence and abundance of parasites, subsequently relating deviations of natural parasite distribution to environmental impact. Metals, often considered pollutants, might occur under natural conditions, where concentrations might be high due to a natural geogenic release rather than anthropogenic activities. We specifically investigated whether naturally occurring high levels of elements might negatively affect the parasite community of the intertidal klipfish, Clinus superciliosus, at different localities along the South African coast. Parasite communities and element concentrations of 55 klipfish (in muscle and liver) were examined. Our results show that parasites can disentangle anthropogenic input of elements from naturally occurring high element concentrations. Acanthocephala, Cestoda and Isopoda were associated with higher concentrations of most elements. Environmental parasitology, applicable to a wide range of systems, is scarcely used on marine ecosystems and can contribute to environmental monitoring programs.

A lentic microcosm approach to determine the toxicity of DDT and deltamethrin on diatom communities.

Worldwide the use of pesticides has increased, especially in the industry and agriculture sector even though they contain highly toxic substances. The use of pesticides has various negative effects on the aquatic ecosystem and organisms within these ecosystems. The paper aimed to assess the effects of increased concentrations of malaria vector control insecticides (Dichlorodiphenyltrichloroethane (DDT) and Deltamethrin (DTM)) on the freshwater diatom community structure using a microcosm approach as well as determine whether a mixture (DDT 1:1 Deltamethrin) exposure will have a greater influence on the diatom community when compared to single exposures of these insecticides. Diatoms were exposed to a high and low concentration (based on LC50 data for freshwater Xenopus laevis from the USEPA Ecotox database) of DDT, DTM and a mixture in lentic microcosms over a total period of 28 days. Results indicated that irrespective of exposure concentrations, DDT, DTM and a mixture had negative effects on the diatom community including functionality and vitality as these insecticides induced changes to their chloroplasts. There was an increased percentage dead cells for all exposures compared to the control, with the insecticides having a phototoxic effect on the diatom community. Exposure to the selected insecticides caused a significant decrease in some diatom metrics indicating the negative effects these insecticides have on the diatom metrics. Therefore, diatoms may prove to be useful as bio-indicators in ecotoxicology studies when assessing the effects of any insecticide exposures.

Metazoan parasite diversity of the endemic South African intertidal klipfish, Clinus superciliosus: Factors influencing parasite community composition.

The current trend in marine parasitology research, particularly in South Africa, is to focus on a specific parasite taxon and not on the total parasite community of a specific fish host. However, these records do not always reveal the ecological role of parasites in ecosystems. Thus, the present study aimed to determine which factors influence the parasite community composition of the endemic southern African intertidal klipfish, Clinus superciliosus (n = 75). Metazoan parasites were sampled from four localities (two commercial harbours - west coast; and two relatively pristine localities - southeast coast) along the South African coast. A total of 75 klipfish were examined for parasites, where 30 distinct taxa, representing seven taxonomic groups were found: Acanthocephala (4 taxa), Cestoda (2 taxa), Crustacea (5 taxa), Digenea (11 taxa), Hirudinea (2 taxa), Monogenea (1 taxon) and Nematoda (5 taxa). Results indicated that the main driver of diversity was locality, with the highest diversity on the southeast coast, most likely due to higher water temperatures and upwelling compared to the west coast. The parasite community composition of the klipfish was significantly influenced by water temperature and parasite life cycle. These results emphasise the importance of parasitological surveys including all parasite taxa in hosts from multiple localities and seasons, to better comprehend their ecological role.

Oxidative stress in the freshwater shrimp Caridina africana following exposure to atrazine.

The toxicity of pesticides to non-target organisms continues to be important in understanding the dynamic interactions between anthropogenic chemicals and ecosystem health. This study assesses biochemical markers to determine the effects that varying concentrations of atrazine (13.1-5557 µg/l) have on the freshwater shrimp, Caridina africana. Exposure and oxidative stress biomarkers were analysed and followed by univariate, integrated biomarker response v2 (IBRv2) and Kendall Tau correlation statistical analyses, to gain insight into the concentration-dependent responses. Oxidative stress biomarkers such as reduced glutathione content (GSH), glutathione-S-transferase activity (GST), superoxide dismutase activity (SOD) and catalase activity (CAT) were significantly correlated with increasing atrazine exposure concentration (p < 0.01). Bimodality has been seen when looking at both the univariate statistically significant differences as well as the IBRv2, with the first peak at 106.8 µg/l and the second peak at 5557 µg/l atrazine. The results indicate that while individual responses may indicate statistically significant differences, using correlation and integrated statistical analysis can shed light on trends in the adaptive response of these.

Drought altered trophic dynamics of an important natural saline lake: A stable isotope approach.

Climate change and associated droughts threaten the ecology and resilience of natural saline lakes globally. There is a distinct lack of research regarding their ecological response to climatic events in the Global South. This region is predicted to experience climatic events such as El Niño-Southern Oscillation (ENSO) more often and with greater severity with the potential to alter the structure and functioning of aquatic ecosystems significantly. From 2015 to 2016 South Africa experienced one of the most severe country-wide droughts as a result of a strong ENSO event. Our study aimed to investigate the effect of this supra-seasonal drought on the trophic structure of fish communities in a naturally saline shallow lake of a Ramsar wetland using stable isotope techniques. Fishes and potential basal sources were collected from the lake, during predrought conditions in 2010 and after severe drought (recovery phase; 2017). The δ13C and δ15N values of food web elements were determined and analysed using Bayesian mixing models and Bayesian Laymen metrics to establish the proportional contribution of C3 and C4 basal sources to the fish (consumer) diets, and examine the fish community in terms of isotopic niche and trophic structure, respectively. Fish consumers relied predominantly on C3 basal sources in the predrought and shifted to greater reliance on C4 basal sources, decreased isotopic niche space use and a reduction in trophic length in the recovery phase. Drought altered the type and abundance of the basal sources available by limiting sources to those that are more drought-tolerant, reducing the trophic pathways of the food web with no significant alterations in the fish community. These results demonstrate the resilience and biological plasticity of Lake Nyamithi and its aquatic fauna, highlighting the importance of freshwater inflow to saline lakes with alterations thereof posing a significant threat to their continued functioning.

Environmentally relevant lead (Pb) water concentration induce toxicity in zebrafish (Danio rerio) larvae.

Early developmental stages of aquatic organisms including fish are inherently vulnerable to lead (Pb) and other water metal contaminants. However, reports on the deleterious effects of environmentally relevant Pb levels are limited. To this end, we exposed 2.5 h post fertilization (hpf) old zebrafish (Danio rerio) embryos to a range of Pb concentrations encompassing environmentally relevant levels (1, 10, 25, 50 and 100 µg/L Pb) until 96 hpf. Exposure negatively impacted the development and survival of zebrafish embryos by inducing embryo coagulation related mortalities in a concentration-dependent manner. At 24 hpf, the highest level of exposure (100 µg/L Pb) had impaired embryo activity characterized by reduced burst activity and the number of movements per minute made by embryos. At 72 hpf, newly hatched larvae exhibited adverse cardiovascular effects (100 µg/L Pb group) and neuromuscular effects (50 and 100 µg/L Pb groups). The antioxidant system dysregulation evidenced by downregulation of catalase, and upregulation of mRNA expression of glutathione S-transferase and cytochrome oxidase subunit I were observed. The pro-apoptotic tumour protein P53 (TP53) and the anti-apoptotic B cell lymphoma -2 (Bcl-2) mRNA expression levels were also affected. The former was downregulated across exposed groups and the latter was upregulated and downregulated in the groups with Pb concentrations less than 50 µg/L Pb and downregulated in 50 µg/L Pb, respectively. These findings suggest that Pb within environmentally relevant levels may be deleterious to developing zebrafish.

Sub-lethal exposure to malaria vector control pesticides causes alterations in liver metabolomics and behaviour of the African clawed frog (Xenopus laevis).

In this study we explore the sub-lethal effects of two malaria vector control pesticides, deltamethrin and dichlorodiphenyltrichloroethane (DDT), on Xenopus laevis by incorporating different levels of biological organisation. Pesticide accumulation in frog tissue was measured alongside liver metabolomics and individual swimming behaviour to assess whether changes presented at these different levels, and if such changes could be linked between levels. Results showed evidence of concentration dependent accumulation of DDT and its metabolites, but no measurable accumulation of deltamethrin in adult X. laevis after 96 h of exposure. Both DDT and deltamethrin were shown to cause alterations in the liver metabolome of X. laevis. We also showed that some of these changes can be enhanced in exposure to a mixture of these two pesticides. Initial behavioural responses recorded directly after exposure were seen in the form of decreased activity, less alterations between mobility states, and less time spent at the water surface. This response persisted after 96 h of exposure to a mixture of the two pesticides. This study shows that sub-lethal exposure to pesticides can alter the biochemical homeostasis of frogs with the potential to cascade onto behavioural and ecological levels in mixture exposure scenarios.

Metal and metalloid concentrations in the southern African endemic inter- and infratidal super klipfish, Clinus superciliosus, from the west and south coasts of South Africa.

Clinus superciliosus was collected for element analysis from six localities along the South African west and south coasts. Concentrations in muscle and liver were determined, considering size and sex. No significant positive correlation between size and concentrations were detected, except for Mn and Sn in liver from Simons Town marina, while no significant differences in sex were detected. The majority of element concentrations were significantly higher in fish from Tsitsikamma in the Garden Route and the small town Chintsa, while some concentrations were significantly higher in muscle at Simons Town marina. Land-use activities had a limited role in element bioaccumulation in klipfish. Element concentrations were influenced by large scale oceanographic processes (currents; upwelling) and localised seasonal geogenic derived run-off. Limited data on element accumulation patterns of intertidal fish species in South Africa, highlights the need for long-term monitoring and further studies on different resident and transient intertidal fish species.

Effects of conventionally-treated and ozonated wastewater on mortality, physiology, body length, and behavior of embryonic and larval zebrafish (Danio rerio).

To date, micropollutants from anthropogenic sources cannot be completely removed from effluents of wastewater treatment plants and therefore enter freshwater systems, where they may impose adverse effects on aquatic organisms, for example, on fish. Advanced treatment such as ozonation aims to reduce micropollutants in wastewater effluents and, thus, to mitigate adverse effects on the environment. To investigate the impact and efficiency of ozonation, four different water types were tested: ozonated wastewater (before and after biological treatment), conventionally-treated wastewater, and water from a river (River Ruhr, Germany) upstream of the wastewater treatment plant effluent. Zebrafish (Danio rerio) embryos were used to study lethal and sublethal effects in a modified fish early life-stage test. Mortality occurred during exposure in the water samples from the wastewater treatment plant and the river in the first 24 h post-fertilization, ranging from 12% (conventional wastewater) to 40% (river water). Regarding sublethal endpoints, effects compared to the negative control resulted in significantly higher heart rates (ozonated wastewater), and significantly reduced swimming activity (highly significant in ozonated wastewater and ozone reactor water, significant in only the last time interval in river water). Moreover, the respiration rates were highly increased in both ozonated wastewater samples in comparison to the negative control. Significant differences between the ozonated wastewater samples occurred in the embryonic behavior and heart rates, emphasizing the importance of subsequent biological treatment of the ozonated wastewater. Only the conventionally-treated wastewater sample did not elicit negative responses in zebrafish, indicating that the discharge of conventional wastewater poses no greater risk to embryonic and larval zebrafish than water from the river Ruhr itself. The sublethal endpoints embryonic- and larval behavior, heart rates, and respiration were found to be the most sensitive endpoints in this fish early life-stage test and can add valuable information on the toxicity of environmental samples.

Metal contamination and toxicity of soils and river sediments from the world's largest platinum mining area.

Mining activities in the world's largest platinum mining area in South Africa have resulted in environmental contamination with Pt (e.g., the Hex River's vicinity). The present study compared a Pt mining area with a non-mining area along this river in terms of (1) metal concentrations in different grain size fractions from soils and aquatic sediments; (2) the toxicological potential of aquatic sediments based on the Consensus-Based Sediment Quality Guideline (CBSQG); and (3) the chronic toxicity of aqueous eluates from soils and sediments to Caenorhabditis elegans. Platinum concentrations were higher in the mining area than in the non-mining area. For most metals, the sediment silt and clay fraction contained the highest metal concentrations. Based on the CBSQG, most sampling sites exhibited a high toxicological potential, driven by Cr and Ni. Eluate toxicity testing revealed that C. elegans growth, fertility, and reproduction inhibition were not dependent on mining activities or the CBSQG predictions. Toxicity was instead likely due to Cd, Fe, Mn, Ni, Pt, and Pb. In conclusion, the investigated region is loaded with a high geogenic background resulting in high reproduction inhibition. The mining activities lead to additional environmental metal contamination (particularly Pt), contributing to environmental soil and sediment toxicity.

Bioaccumulation of DDT and other organochlorine pesticides in amphibians from two conservation areas within malaria risk regions of South Africa.

The threat to wildlife from chemical exposure exists regardless of the presence of conservation boundaries. An issue exacerbated by the use of environmentally persistent insecticides for vector control and long-range transport of legacy persistent organic pollutants. In this comparative study between two important conservation regions in South Africa, Kruger National Park (KNP) and Ndumo Game Reserve (NGR), we assessed organochlorine pesticide (OCP) accumulation in several anuran species collected from within the conservation regions. The two conservation regions differ in size and subsequent proximity of collection sites to OCP input sources. Detectable concentrations of OCPs were present in ∼ half the frogs analysed from KNP and ∼all frogs from NGR and total OCP loads were similar between regions, where measured in the same species. The OCP profiles in KNP frogs were representative of legacy pesticides likely introduced via long-range transport, whereas NGR profiles showed influence of current use of DDT consistent with close proximity to sources. This indicates amphibians can accumulate OCPs within conservation regions and that the exposure of non-target organisms inside conservation regions to current use pesticides has a strong association with proximity to sources. These results serve to inform conservation management decision making with regard to the non-target organism effects of chemical interventions such as vector control pesticide use in and around conservation regions.